Light-emitting diodes (LEDs) can effectively convert electrical energy into light. However, the characteristics of the light which is emitted by different but nominally equal LEDs under the same operating conditions can vary due to a number of different factors which can be caused by, for example, variations in device manufacturing and device assembly. These variations can exceed the requirements imposed by those LED illumination applications which can require that the light emitted from two or more LEDs closely match. This can be particularly important for spatially extended luminaires in which the use of varying output intensity LEDs is undesired. Close binning or matching of individual nominally equal LEDs, while possible, can render many LED-based general purpose illumination systems substantially cost-ineffective.
An alternative solution which can be used to mitigate the effects of variations in light emission characteristics in nominally equal LEDs is described in U.S. Pat. No. 4,743,897, which describes an LED driver circuit including a current source for generating a constant drive current to a plurality of series connected LEDs, circuitry for selectively enabling and disabling predetermined ones of the LEDs and further circuitry for disabling the current source in the event none of the LEDs are enabled. While the LED driver circuit is of simple design and low cost, and is characterized by relatively low power consumption in comparison to other solutions, the energy efficiency and operational characteristics of this LED driver circuit can be limited.
Therefore, there is a need for a new light-emitting element control system, and lighting system comprising same, that overcomes some of the drawbacks of know systems.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.